Gastric ulcers are a defect in the stomach lining. Some of the cells that line the stomach produce hydrochloric acid. This acid helps to break down the food in the stomach so that nutrients in the food can be digested by the body.

Sometimes, the acid in the stomach causes erosion or defects in the stomach wall and these are known as gastric ulcers. Unlike in humans, gastric ulcers in horses are not caused by bacteria.

What causes gastric ulcers? 

The causes of gastric ulcers are many and varied and are usually grouped under the broad heading of stress. A few of the factors that may predispose horses to gastric ulcers are:

•    Stabling is recognised to be a source of stress to horses

•    Inadequate roughage intake. The cells lining the stomach secrete hydrochloric acid all the time. This means that feeding high grain diets a couple of times a day with only low levels of roughage can lead to the stomach being exposed to hydrochloric acid without the protection from roughage that occurs when a horse is grazing

•    Extreme athletic performance can lead to reduced blood flow to the stomach meaning that racehorses are at an increased risk

•    Some drugs e.g., phenylbutazone can cause gastric ulcers

How are gastric ulcers diagnosed?

Horses with gastric ulcers can present with colic that will often reoccur. However, the outward signs shown by a horse with gastric ulcers vary widely and so there is no specific set of signs that will indicate that a horse has a gastric ulcer.

Poor performance, reduced appetite, and difficulty in maintaining good body condition can be seen with gastric ulcers. However, to make a diagnosis of gastric ulcer, a camera with a light on the end of a tube (an endoscope) is needed to visualize the stomach lining.

How are gastric ulcers treated?

Many strategies can be put into play to prevent gastric ulcers from occurring as described above under ‘What causes gastric ulcers?’

Essentially all steps that can be taken to minimise stress and to improve the stomach’s health will help to avoid the development of gastric ulcers e.g., providing adequate roughage by ensuring access to grass or hay when possible.

A range of products are available on the market for treating gastric ulcers, but they should only be used in consultation with your veterinarian after a diagnosis has been made.


Gastric ulcers are very common in the equine athlete. If you are concerned a horse may be affected, seek the advice of your veterinarian to ensure diagnosis and an effective management and treatment plan.